Fabrication of Frog-Skin-Inspired Slippery Antibiofouling Coatings Through Degradable Block Copolymer Wrinkling

Marine biofouling is a severe problem with a wide-reaching impact on ship maintenance, the economy, and ecosystem safety, among others. Inspired by complex multifunctional frogskins, wrinkled slippery coatings are created that exhibit remarkable antifouling, anti-icing, and self-cleaning properties through a combination of degradable di-block copolymer self-assembly [i.e., polystyrene-b-polylactide (PS-b-PLA)] and hydrolysis-driven dynamic release-induced surface wrinkling. Microwrinkled patterns can generate curved surfaces that are resistant to biofouling. Gyroid-forming PS-b-PLA can be used to produce nanoporous templates with cocontinuous nanochannels, which generate strong capillary forces for trapping and storing infiltrated lubricants. In this study, block-copolymer-derived hierarchically wrinkled slippery liquid-infused nanoporous surfaces (i.e., micro wrinkles with nanochannels infused with slippery fluids) are successfully fabricated after silicone oil infiltration. The antibiofouling performance of these surfaces is examined against different foulers under various conditions. The produced coatings exhibited flexible, stable, transparent, and easily tunable antibiofouling characteristics. In particular, the formation of an eco-friendly silicon-based lubricant layer without the use of fluorinated compounds and costly material precursors is an advantage in industrial practice that can be adopted in various applications, such as fuel transport, self-cleaning windows, anticorrosion protection, nontoxic coatings for medical devices, and optical instruments.     

Inherently UV Photodegradable Poly(methacrylate) Gels

Organogels (hydrophobic polymer gels) are soft materials based on polymeric networks swollen in organic solvents. They are hydrophobic and possess a high content of solvent and low surface adhesion, rendering them interesting in applications such as encapsulants, drug delivery, actuators, slippery surfaces (self-cleaning, anti-waxing, anti-bacterial), or for oil-water separation. To design functional organogels, strategies to control their shape and surface structure are required. Herein, the inherent UV photodegradability of poly(methacrylate) organogels is reported. No additional photosensitizers are required to efficiently degrade organogels (d ≈ 1 mm) on the minute scale. A low UV absorbance and a high swelling ability of the solvent infusing the organogel are found to be beneficial for fast photodegradation, which is expected to be transferrable to other gel photochemistry. Organogel arrays, films, and structured organogel surfaces are prepared, and their extraction ability and slippery properties are examined. Films of inherently photodegradable organogels on copper circuit boards serve as the first ever positive gel photoresist. Spatially photodegraded organogel films protect or reveal copper surfaces against an etchant (FeCl_{3 aq.}).     

Stable Omniphobic Anisotropic Covalently Grafted Slippery Surfaces for Directional Transportation of Drops and Bubbles

Directional transportation and collection of liquids and bubbles are highly desirable in human life and industrial production. As one of the most promising types of functional surfaces, the reported anisotropic slippery liquid‐infused porous surfaces (SLIPSs) demonstrate unique advantages in liquid directional transportation. However, anisotropic SLIPSs readily suffer from the depletion of lubricant when used to manipulate droplets and bubbles, which leads to unstable surface properties. Therefore, fabricating stable anisotropic slippery surfaces for the directional transportation of drops and bubbles remains a challenge. Here, stable anisotropic covalently grafted slippery surfaces are fabricated by grafting polydimethylsiloxane molecular brushes onto directional microgrooved surfaces. The fabricated surfaces show remarkable anisotropic omniphobic sliding behaviors towards droplets with different surface tensions ranging from 72.8 to 37.7 mN m^?1 in air and towards bubbles underwater. Impressively, the surface maintains outstanding stability for the transportation of droplets (in air) and air bubbles (underwater) even after 240 d. Furthermore, anisotropic self‐cleaning towards various dust particles in air and directional bubble collection underwater are achieved on this surface. This stable anisotropic slippery surface has great potential for applications in the directional transportation of liquids and bubbles, microfluidic devices, directional drag reduction, directional antifouling, and beyond.     

Magnetocontrollable Droplet and Bubble Manipulation on a Stable Amphibious Slippery Gel Surface

Smart manipulation of liquid/bubble transport has garnered widespread attention due to its potential applications in many fields. Designing a responsive surface has emerged as an effective strategy for achieving controllable transport of liquids/bubbles. However, it is still challenging to fabricate stable amphibious responsive surfaces that can be used for the smart manipulation of liquid in air and bubbles underwater. Here, amphibious slippery surfaces are fabricated using magnetically responsive soft poly(dimethylsiloxane) doped with iron powder and silicone oil. The slippery gel surface retains its magnetic responsiveness and demonstrates strong affinity for bubbles underwater but shows small and switching resistance forces with the water droplets in air and bubbles underwater, which is the key factor for achieving the controllable transport of liquids/bubbles. On the slippery gel surface, the sliding behaviors of water droplets and bubbles can be reversibly controlled by alternately applying/removing an external magnetic field. Notably, compared with slippery liquid‐infused porous surfaces, the slippery gel surface demonstrates outstanding stability, whether in air or underwater, even after 100 cycles of alternately applying/removing the magnetic field. This surface shows potential applications in gas/liquid microreactors, gas–liquid mixed fluid transportation, bubble/droplet manipulation, etc.     

Programmable Droplet Bouncing on Bionic Functional Surfaces for Continuous Electricity Generation

The natural phenomenon of droplets bouncing on various surfaces holds remarkable potential for applications like water transportation, self-cleaning, antifreezing, etc. However, achieving precisely controlled patterned droplet bouncing on functional surfaces with accurately controlled factors like bouncing velocity and trajectory in three dimensions remains a formidable challenge. In this context, a concept of bionic hydrophobic functional surfaces composed of mushroom-like microstructures is introduced. These microstructures are crafted using the projection microstereolithography (PµSL) based 3D printing technique, subsequently coated with a hydrophobic spray. By finely adjusting the geometric attributes and inclination angles of these micromushrooms, the ability is gained to meticulously manipulate the bouncing velocity and trajectory of water droplets. The most optimal performance is demonstrated by a droplet exhibiting a maximal jumping distance and height respectively of 2.5 and 7.1 mm with 50° inclined micromushrooms. Notably, these specially designed micromushrooms orchestrate diverse behaviors in droplet bouncing, encompassing patterned bouncing, antigravity jumps, and directional water transportation. Additionally, the functional surface's adaptable self-cleaning capability facilitates the harnessing of energy from rainfall on large surfaces, offering potential applications in realms, such as self-cleaning mechanisms, droplet capture, water conveyance, and clean energy generation.     

Transparent Superamphiphobic Material Formed by Hierarchical Nano Re-Entrant Structure

Developing transparent and superamphiphobic materials that can repel low-surface-tension liquids is attractive for fundamental research and industrial applications. Despite great progress, it remains a daunting challenge to scalably fabricate highly transparent superamphiphobic materials because of the inherent paradox in surface roughness to achieve superamphiphobicity and optical transparency. Herein, a scalable template-assisted spray coating method is developed to form hierarchical nano re-entrant structures that eliminate the visible-light scattering while maintaining optical transmittance above 88% in the visible region, besides retaining the superamphiphobicity to various low surface-tension liquids. In addition to exhibiting improved mechanical, chemical, and thermal stabilities, these transparent superamphiphobic materials can also be applied on various substrates, including curved surfaces and solar panels, to enhance their optical stability. This study believes that these excellent overall properties possess enormous potential for various applications involving self-cleaning, anti-fouling, and anti-counterfeiting.     

High-Resolution Patterned Functionalization of Slippery “Liquid-Like” Brush Surfaces via Microdroplet-Confined Growth of Multifunctional Polydopamine Arrays

Slippery omniphobic covalently attached liquids enable smooth, transparent, pressure- and temperature-resistant, and liquid-repellent coatings. Patterned functionalization of such surfaces would drive technology developments and fundamental understandings in broad applications from biosensors to sustainable smart surfaces. Herein an additive microcontact printing approach in combination with the microdroplet-confined synthesis is developed to functionalize slippery surfaces tethered with “liquid-like” linear poly(dimethylsiloxane) by multifunctional polydopamine (PDA) arrays. Using glycerol and non-ionic surfactant Tween-20, microdroplet arrays containing dopamine monomers are printed onto the slippery surfaces and serve as microreactors for the in situ growth of PDA micropatterns. The confined growth approach enables tunable feature size, height, and morphology of the patterns, through which sub-micrometer PDA dot arrays over centimeter-square patterning area can be reliably achieved. Furthermore, the reactive and hydrophilic PDA micropatches allow further functionalization of the slippery surfaces with a diverse variety of materials, meanwhile the anti-fouling and dynamically dewetting “liquid-like” brushes permit minimum background contamination. Proof-of-concept demonstrations include PDA-initiated photografting for stimuli-responsive polymer functionalization, protein immobilization for microarray-based immunoassays, as well as sliding-induced selective dewetting of organic solutions to pattern photoluminescent perovskite microcrystals and nanoparticles. The current approach illustrates the potential for applying patterned slippery surfaces with multifunctional architectures in many fields.     

Tunable Structural Color Surfaces with Visually Self‐Reporting Wettability

Functional materials with wettability of specific surfaces are important for many areas. Here, a new lubricant‐infused elastic inverse opal is presented with tunable and visually “self‐reporting” surface wettability. The elastic inverse opal films are used to lock in the infused lubricating fluid and construct slippery surfaces to repel droplets of various liquids. The films are stretchable, and the lubricating fluid can penetrate the pores under stretching, leaving the surface layer free of lubrication; the resultant undulating morphology of the inverse opal scaffold topography can reversibly pin droplets on the fluidic film rather than the solid substrate. This mechanical stimulation process provides an effective means of dynamically tuning the surface wettability and the optical transparency of the inverse opal films. In particular, as the adjustments are accompanied by simultaneous deformation of the periodic macroporous structure, the inverse opal films can self‐report on their surface status through visible structural color changes. These features make such slippery structural color materials highly versatile for use in diverse applications.     

Slippery Liquid‐Infused Porous Surfaces that Prevent Microbial Surface Fouling and Kill Non‐Adherent Pathogens in Surrounding Media: A Controlled Release Approach

Many types of slippery liquid‐infused porous surfaces (‘SLIPS’) can resist adhesion and colonization by microorganisms. These ‘slippery’ materials thus offer approaches to prevent fouling on commercial and industrial surfaces. However, while SLIPS can prevent fouling on surfaces to which they are applied, they can currently do little to prevent the proliferation of non‐adherent organisms. Here, multi‐functional SLIPS are reported that address this issue and expand the potential utility of these materials. The approach is based on the release of antimicrobial agents from the porous matrices used to host the infused oil phases. It is demonstrated that SLIPS fabricated from nanoporous polymer multilayers can prevent colonization and biofilm formation by four common fungal and bacterial pathogens, and that the polymer and oil phases comprising these materials can be used to sustain the release of triclosan, a model antimicrobial agent, into surrounding media. This approach improves the inherent anti‐fouling properties of these materials and endows them with the ability to kill non‐adherent pathogens. This strategy has the potential to be general; the strategies and concepts reported here will enable the design of SLIPS with improved anti‐fouling properties and open the door to new applications of slippery liquid‐infused materials that host or release other active agents.     

Slippery Lubricant‐Infused Surfaces: Properties and Emerging Applications

Bioinspired lubricant‐infused surfaces exhibit various unique properties attributed to their liquid‐like and molecularly smooth nature. Excellent liquid repellency and “slippery” properties, self‐healing, antiicing, anticorrosion characteristics, enhanced heat transfer, antibiofouling, and cell‐repellent properties have been already demonstrated. This progress report highlights some of the recent developments in this rapidly growing area, focusing on properties of lubricant‐infused surfaces, and their emerging applications as well as some future challenges.     

Design of Variable-friction devices for shoe-floor contact

In rehabilitation training, high-fidelity simulation environments are needed for reproducing the effects of slippery surfaces, in which potential balance failure conditions can be reproduced on demand. Motivated by these requirements, this article considers the design of variable-friction devices for use in the context of human walking on surfaces in which the coefficient of friction can be controlled dynamically. Various designs are described, aiming at rendering low-friction shoe-floor contact, associated with slippery surfaces such as ice, as well as higher-friction values more typical of surfaces such as pebbles, sand, or snow. These designs include an array of omnidirectional rolling elements, a combination of low- and high-friction coverings whose contact pressure distribution is controlled, and modulation of low-frequency vibration normal to the surface. Our experimentation investigated the static coefficient of friction attainable with each of these designs. Rolling elements were found to be the most slippery, providing a coefficient of friction as low as 0.03, but with significant drawbacks from the perspective of our design objectives. A controlled pressure distribution of low- and high-friction coverings allowed for a minimum coefficient of friction of 0.06. The effects of vibration amplitude and frequency on sliding velocity were also explored. Increases in amplitude resulted in higher velocities, but vibration frequencies greater than 25 Hz reduced sliding velocities. To meet our design objectives, a novel approach involving a friction-variation mechanism, embedded in a shoe sole, is proposed.     

Ultradurable Omni-Liquid-Repellent Smart Window as a High-Performance Wettability/Transparency Manipulator Enabled via Laser-Writing Magnetism-Actuated Microshutters

Slippery liquid-infused porous surfaces (SLIPS) derived smart windows (SWs) that dynamically fine-tune the solar spectrum are promising candidates for alleviating the global energy crisis, especially for dim rainy climates. Unfortunately, the inferior durability, high energy-consumption, and slow tune-responsivity over SLIPS-based SWs greatly hinder their practical usage. Reported is an ultrarobust omni-liquid-repellent magnetism-actuated reconfigurable microshutters (OLR-MARS) via integrating a femtosecond laser ablation and soft-lithography technique. By alternately loading/discharging a remote magnet, OLR-MARS can be reversibly switched between a transparent mode and an opaque mode within 0.03 s, which is far sensitive than the previously-reported SWs. Simultaneously, OLR-MARS can harness the surface liquids between a slippery state (the sliding angle of ≈15^o) and a sticky one (pinning at a tilt angle of 90^o). Significantly, owing to its all-solid-state merit, OLR-MARS demonstrates good longevity even when subjected to the raindrops impact above 1000 cycles. Results indicate dual switching over the interfacial hydrodynamics and optics. Last but not least, leveraging the optimized OLR-MARS, encryption-decryption, thermal management, and an angle-dependent privacy-screen is deployed. Current novel OLR-MARS with robust durability, fast responsivity, and energy-free advantages holds promising potential in self-cleaning smart windows, energy-saving buildings, antivoyeurism, etc.     

Long-Term Super-Amphiphilic Shaped-Fiber with Multi-Scale Grooved Structures: Toward Spontaneous Self-Cleaning

Despite long-term exposure to the ambient environment, fabrics made of bamboo fibers enable spontaneous self-cleaning of oil contaminants without using any surfactant. Here, it is revealed that the long-term stable super-amphiphilicity of bamboo fibers is responsible for self-cleaning behavior. Liquids of both water and oil are liable to super-spread on bamboo fibers, driven by multi-scaled capillary forces imparted by the unique shaped fibrous structures with multi-scale hierarchical ridges/grooves. Based on the minimization of free energy, the pre-wetted oils can be easily removed away by forming the water film, reaching the spontaneous self-cleaning. Notably, the super-amphiphilicity induced by the structure shows better long-term stability compared with that endowed by chemical modification. It is demonstrated that the bio-inspired artificial counterpart also exhibits excellent self-cleaning property, which inspires innovative self-cleaning textures.     

瓷绝缘子表面激光损伤的数值模拟和实验研究

为了防止输电线路激光除冰过程中激光损伤绝缘子等电力设备,采用有限元分析软件ANSYS对激光与普通瓷、氧化铝瓷、氧化锆瓷、堇青石瓷作用后的温度场和应力场进行了数值模拟,得到氧化铝瓷具有较好的抗热应力破坏性能,并进行了Nd∶ YAG激光照射绝缘子表面实验,得到绝缘子表面温度与照射时间和损伤类型的关系.结果表明,激光功率密度...     

Overcoming Limitations in Surface Geometry-Driven Bubble Transport: Bidirectional and Unrestricted Movement of an Underwater Gas Bubble Using a Magnetocontrollable Nonwetting Surface

The movement of underwater gas bubbles significantly affects the core processes of a variety of applications in water electrolysis, heat transfer, optofluidics, and other fields. To maneuver the motion of bubbles, surface geometry-driven transport is widely applied by employing asymmetric nonwetting surfaces, which induce Laplace pressure based on the bubble radius differences in confined states. Although this method has successfully demonstrated bubble manipulations in various geometries, it has inevitably shown some critical limitations; gas bubbles move unidirectionally from tip to root direction and cease their movements upon reaching unconfined states. This unidirectional and local bubble transport restrains the method's applicability to many fields, and overcoming this obstacle still remains an enormous challenge. Herein, a magnetocontrollable lubricant-infused surface (MCLIS) is introduced as a key solution to this issue. MCLISs manipulate the adhesion of gas bubbles by controlling magneto-responsive microwire alignments and rendering two reversible adhesion states, sticky (upright) and slippery (laying wires). This unique characteristic of MCLISs enables the bidirectional and geometry-unrestricted transportation of bubbles by the wire geometry-gradient force (F_wgg) generated at sticky–slippery interfaces. Furthermore, this novel magnetic responsive surface supports anti-buoyancy transport and presents promising applications in microreactors and optical laser shutters in aqueous media.     

Spot-size converted 1.3 μm laser with butt-jointed selectivelygrown vertically tapered waveguide

A 1.3 μm laser has been developed with a butt-jointed selectively grown spot-sire converter (SSC). The SSC vertically tapered waveguide and strained multiquantum well (MQW) active region are independently optimised. The laser was buried with semi-insulating InP to reduce optical loss in the SSC. A threshold current of 7 mA and an output power of >20 mW were obtained. Minimum coupling loss to a flat-end fibre of 1.06 dB was achieved. Long-term stability was also confirmed     

Skin-Inspired Nanofluid-Filled Surfaces with Tunable Icephobic,Photothermal, and Energy Absorption Properties

Ice buildup can significantly and negatively impact system performance in various industrial sectors, and has remained a persistent challenge for decades. Many compliant materials exhibit excellent de-icing performance but are easily eroded by impacts from supercooled water droplets, sand, dust, and debris. A composite panel inspired by animal skin, consisting of a facesheet protecting a nanofluid layer beneath, which exhibits durable anti-icing and tunable photothermal properties is proposed. The viscous liquid layer beneath the facesheet increases flexural rigidity, preventing large deflections and increasing deformation resistance, which alters ice's adhesion to the surface. The non-uniform fluid pressure exerted by the viscous nanofluid-filled composite panels facilitates ice detachment, resulting in ice adhesion strengths as low as τ_ice ≈ 10 kPa. Further, by altering the fluid properties, different additional functionalities can be endowed to the system. Incorporating fumed silica in a fluid-filled composite panel results in rheopectic behavior, and this doubles their impact resistance when the shear thickening properties are properly tuned. Additionally, the combination of a transparent facesheet and a solar light absorbent nanofluid allows for tunable photothermal properties, further enhancing the anti-icing performance of the system. This durable and tunable nanofluid-filled composite panel shows great promise as a multifunctional de-icing material.     

Freezing as a Path to Build Micro-Nanostructured Icephobic Coatings

Superhydrophobic photothermal materials with the micro-nano structure are considered to be promising icephobic surfaces. Unfortunately, converting micro-nano hierarchical structure concepts into genuine synthetic materials has proven to be exceedingly expensive and difficult, partially because their sophisticated structures need construction at several length scales. Herein, a facile strategy of employing ice crystals to construct sophisticated hierarchical micro-nanostructured anti-icing composites with photothermal, self-healable, and self-cleaning properties is presented. The composites are covered with interconnected microscale pores replicated from ice crystals, which facilitates the construction of the hydrophobic or superhydrophobic properties based on the Cassie–Baxter model, endowing the coating with self-cleaning ability. Besides, by adding solar-to-heat conversation nanomaterials, the coating can implement in situ solar anti-/deicing. The abundant micropores caused by ice templates can further improve the photothermal conversion capability through multiple reflections of light. Importantly, the coating is endowed with the self-healing capability to repair hydrophobicity under sunlight. Additionally, it is demonstrated that the self-cleaning and self-healing abilities are mutually reinforcing, synergistically improving anti-/deicing performances. Overall, the presented ice-templated coating shows great potential and broad impacts owing to its inexpensive component materials, simplicity, eco-friendliness, and high energy efficiency.     

Two-Dimensional Siloxene–Graphene Heterostructure-Based High-Performance Supercapacitor for Capturing Regenerative Braking Energy in Electric Vehicles

The development of high-performance electrodes that increase the energy density of supercapacitors (SCs) (without compromising their power density) and have a wide temperature tolerance is crucial for the application of SCs in electric vehicles. Recent research has focused on the preparation of multicomponent materials to form electrodes with enhanced electrochemical properties. Herein, a siloxene–graphene (rGO) heterostructure electrode-based symmetric SC (SSC) is designed that delivers a high energy density (55.79 Wh kg⁻¹) and maximum power density of 15 000 W kg⁻¹. The fabricated siloxene–rGO SSC can operate over a wide temperature range from –15 to 80 °C, which makes them suitable for applications in automobiles. This study shows the practical applicability of siloxene–rGO SSC to drive an electric car as well as to capture the braking energy in a regenerative brake-electric vehicle prototype. This work opens new directions for evaluating the use of siloxene–rGO SSC as suitable energy devices in electric vehicles.     

Tilting‐Sensitive Triboelectric Nanogenerators for Energy Harvesting from Unstable/Fluctuating Surfaces

The invention of triboelectric nanogenerators provides an opportunity to utilize previously wasted mechanical energy. The sway energy of ships that affects navigation and comfort on board has been considered negative in the past. Here, a tilting‐sensitive triboelectric nanogenerator (TS‐TENG) that can effectively harvest energy from unstable/fluctuating surfaces is demonstrated by using the sway energy of ships. The device adopts integrated blade structures on sliders, which make it sensitive to tilts and guarantee its power output. The response of the device to tilt agitations of different slopes and frequencies is systematically investigated. Rotational symmetry configuration is used to improve the motion stability of the device by excluding extra torque on the sliders. The peak power density and average power density of the TS‐TENG can reach 1.41 and 0.1 W m^?3, respectively, in low‐frequency and low‐amplitude fluctuating conditions. By the excellent performance of harvesting energy from unstable/fluctuating surfaces, the TS‐TENG is considered promising for powering various distributed sensor devices on the ship for smart ships.